Strollers for carrying a baby have been conventionally, generally used. There are various requirements for strollers depending on their intended uses. For example, in order that a stroller can safely place thereon a baby, the stroller is required to have a high rigidity and a stability during traveling. In addition, in order that a stroller can smoothly travel on a complicated route, the stroller is required to be have a small turning circle, and to be easy to maneuver. Further, in consideration of a storage space when not used, it is required that a stroller is foldable and that the stroller is small in size. In addition, when the stroller is foldable, the stroller is required to be easily folded. In order to meet these requirements, various strollers have been proposed (for example, JP2007-537911T).
However, to simultaneously meet these various requirements obliges a stroller to have contradictory structures. For example, in order that a stroller has a high rigidity, the size of the stroller is enlarged, which is disadvantageous in storage. Thus, the various strollers which have been proposed heretofore cannot simultaneously meet each of the various requirements at a satisfactory level.